BUG #5728: Unexpected behavior comparing result of age() to an interval

The following bug has been logged online:

Bug reference: 5728
Logged by: Dobes Vandermeer
Email address: dobes(dot)vandermeer(at)kashoo(dot)com
PostgreSQL version: 8.4
Operating system: Windows
Description: Unexpected behavior comparing result of age() to an
interval
Details:

Seeing some surprising behavior with the use of age() and comparing the
result to an interval:

select current_date,
age(current_date - interval '123 days') <= interval '120 days',
age(current_date - interval '122 days') <= interval '120 days',
age(current_date - interval '121 days') <= interval '120 days',
age(current_date - interval '120 days') <= interval '120 days',
age(current_date - interval '62 days') <= interval '60 days',
age(current_date - interval '61 days') <= interval '60 days',
age(current_date - interval '60 days') <= interval '60 days',
age(current_date - interval '30 days') <= interval '30 days';

Returns:

"2010-10-26";f;t;t;t;f;t;t;t

But I expected:

"2010-10-26";f;f;f;t;f;f;t;t

Something fishy there ...